1. Field of the Invention
The present invention relates to a paper feeding apparatus for printer for feeding the copy paper held in a paper tray to a printing portion.
2. Description of the Related Art
As an apparatus of the described type for use for example in an ink jet printer, there has been known one in which paper held in a paper tray is brought into abutment with a feed roller by rotation of the paper tray round its fulcrum so that the paper is fed to the printing head by means of the rolling friction of the feed roller and printed by the printing head. General arrangement of an example of the apparatus with the described arrangement is shown in FIG. 11 to FIG. 13.
In a printer body 1, there are disposed in predetermined positions a printing head 3 as the ink jet head, a paper setting mechanism 10, and a paper feeding mechanism 20.
The paper setting mechanism 10 includes a paper tray 11 arranged in the printer body 1 for rotation round a fulcrum 12 and having a paper holding portion 80 holding plural sheets of paper. The paper setting mechanism 10 is arranged to set paper in a feeding position by rotating the paper tray 11 in the direction of the arrow F a predetermined angle from the standby position shown in FIG. 11 thereby bringing the paper held in the paper tray 11 into abutment with a feed roller 21. More specifically, the paper setting mechanism 10 includes, other than the paper tray 11, a spring 13 which urges the paper tray 11 toward the feed roller 21 so that the topmost sheet of paper held in the paper tray 11 abuts on the feed roller 21 and a cam member 14 which, by being rotated in a predetermined direction (for example, in a clockwise direction), presses the paper tray 11 through a cam-contacted surface 11c, against the urge of the spring 13, so that the paper tray 11 is rotated in the direction to go away from the feed roller 21. The cam member 14 is generally formed of a synthetic resin for easiness of its fabrication and other reasons.
The paper setting mechanism 10 is driven by a drive mechanism for paper setting 30 shown in FIG. 12. The drive mechanism for paper setting 30 includes a paper setting motor 31 and a gear train (a pinion gear 32 and a cam gear 33) for transmitting the driving force of the paper setting motor 31 to the cam member 14 so that the cam member 14 is rotated in the clockwise direction in the drawing. Therefore, by rotating the cam member 14 a predetermined angle in the clockwise direction using the drive mechanism for paper setting 30, the paper held in the paper tray 11 can be brought into contact with the feed roller 21 or separated therefrom. The position of the cam member 14 is detected by a cam sensor, not shown, and, it is adapted such that the position of the paper and the paper tray 11 can be determined according to the result of the detection.
The paper feeding mechanism 20 is arranged so as to feed the paper to a position confronting the printing head 3. In concrete terms, the paper feeding mechanism 20, as shown in FIG. 11 and FIG. 13, includes the feed roller 21 and a leaf plate 23 to press the paper against the feed roller 21.
The paper feeding mechanism 20 is driven by a drive gear mechanism for paper feeding 40 shown in FIG. 12. The drive gear mechanism for paper feeding 40 includes a paper feeding motor 41 and a gear train (a pinion gear 42, intermediate gears 43, 44, and 45, and a driven gear 46) for transmitting rotating power of the paper feeding motor 41 to the feed roller 21. Accordingly, when the paper tray 11 having the paper in its set state (where the topmost sheet of paper held in the paper tray 11 is in abutment with the feed roller 21) as shown in FIG. 13, if the paper feeding motor 41 of the drive gear mechanism for paper feeding 40 is driven so that the feed roller 21 is rotated clockwise, the topmost sheet of paper is fed by the feed roller 21 and transported to the ink jet head 3.
After the top end of the copy paper fed out of the paper tray 11 has reached the leaf plate 23, the paper setting motor 31 is driven so that the paper tray 11 is rotated downward and positioned in its standby position shown in FIG. 11. The paper picked up between the leaf place 23 and the feed roller 21 is fed to the printing head 3 and it, after being printed, is delivered to a paper receiving portion 7 by a delivery roller 5 and a pinch roller 6.
The portion of the paper tray 11 coming into contact with the feed roller 21 is precisely finished into a plane surface and, in addition, provided with a high friction coefficient by having cork or the like attached thereto so that the final sheet of paper can be given a sufficient frictional force. The whole body of the paper tray 11, while it is designed to be small and light, is formed of a highly rigid material to prevent the paper from unevenly abutting on the feed roller 21. It is usually formed of an aluminum die casting. Thus, the paper tray 11 is prevented from deforming in the direction rectangular to the paper feed direction or the like and, thereby, the paper tray 11 is pressed against the feed roller 21 with uniform pressure. As a result, the paper held in the paper tray 11 is prevented from making for example diagonal movement and hence it is smoothly fed. Further, the cam-contacted surface 11c of the paper tray 11 is formed of a sliding material (for example, a synthetic resin) separate from the paper tray 11 so that the cam member 14 formed of a synthetic resin may not be worn out in a short period of time.
Problems in such related art will be described below. In the field of printers such as ink jet printers, there have recently been great demands for apparatus in smaller size. Accordingly, attempts are being made, concerning the paper feeding apparatus for the printer, to make the bulky constituents, such as the drive mechanism for paper setting 30 and the drive gear mechanism for paper feeding 40, into smaller size or to change layout of these mechanisms so as to save installing space of them. However, there is a problem that the demands for smaller-sized apparatus cannot fully be met by such designating. Also, it is a problem that cost for parts is high because two independent systems are required for the drive system of the drive mechanism for paper setting 30 and the drive system of the drive gear mechanism for paper feeding 40.